Right now I am farming for the Crawling Claw and the Hyacinth Macaw but it took me several months of farming to get the disgusting oozeling. The absolute worst for me was the Giant Sewer Rat took me from the start of Wrath till just a couple months ago to get him. Hours and hours of fishing... watching people next to me get the achivement. I deeply fear the the same fate for the SeaPony

None that I actually have any control over obtaining. Small guild, means that hampers me greatly on one pet and excludes me from another. I'll just have to hope in the next expansion the legendary pet isn't removed from the achievement and my small group will be able to do the questline for someone.

Frigid Frostling for me, as well. Actually, before 4.3 it was the only pet I hadn't collected, excluded pets aside. Of course, I never missed a summon, but I just wasn't lucky enough to fine one in my satchel Maybe next year I can buy it for blossoms.

While I don't have the crawling claw like most of you, I haven't really tried that hard to get it. The two that elude me the most are the Fox Kit simply because I can't stand the idea of it all: (morbid alert) you hunt down and kill hundreds pregnant fox mothers and essentially cut them open to get their unborn babies out of them. It's just so disgusting that I can't bring myself to do it (yes they're pixes but the principle bothers me). And then there's the Kirin Tor Familiar just due to the whole "out of sight out of mind" mentality since we aren't in Dalaran anymore.